1. Field of the Invention
The present invention generally relates to methods and apparatus for stimulating certain areas of the brain to treat eating disorders by modulation of electrical activity of neural tissue in the selected area of the brain.
2. Description of Related Art
When a person's eating behavior is disordered to such an extent that the individual's physical health is detrimentally affected, the condition is termed an eating disorder. The most familiar types of eating disorders are bulimia nervosa and anorexia nervosa. Bulimia nervosa (“bulimia”) is an eating disorder in which an individual experiences recurrent episodes of insatiable craving for food often resulting in episodes of binge eating followed by inappropriate compensatory behavior to prevent weight gain. The inappropriate compensatory behavior typically includes self-induced vomiting, fasting, excessive exercise, and use of laxatives and diuretics. People suffering from bulimia commonly engage in binge eating and inappropriate compensatory behavior an average of two times a week for a period of three or more months. It has been reported that as many as 17% of college-age women engage in bulimic behaviors, although their weight is usually normal or slightly above. Anorexia nervosa is characterized by voluntary starvation which may be combined with exercise stress. An anorexic individual maintains a body weight that is below a minimally normal level for age and height. Binge eating, without compensatory purging behavior, is also a type of eating disorder characterized by consuming large quantities of food, or eating inappropriate food in secret, and weight gain.
Eating disorders have both physical and psychological components, and it has been said that eating disorders are not about food, but food is the tool that people with eating disorders abuse. Severe medical complications can develop as a consequence of an eating disorder. An eating disorder may be mild in one person and severe or even life threatening in another. Typically, an affected individual will attempt to hide his or her abnormal behavior from others, and may reject diagnosis of an eating disorder or avoid treatment.
In the human body, food intake is controlled by a complex interaction of internal and external stimuli. It is known that the vagus nerve plays a role in mediating afferent information from the stomach to the satiety centers of the brain. U.S. Pat. No. 5,188,104 (Cyberonics, Inc.) and U.S. Pat. No. 5,263,480 (Cyberonics, Inc.) disclose methods of treating eating disorders, including bulimia, that include sensing the quantity of food consumed by the patient in a predetermined period of time, and, if the consumption exceeds a predetermined level in that time period, applying a stimulating signal to the patient's vagus nerve. The output signal parameters of the neurostimulator's stimulus generator are programmed to stimulate vagal activity in such a way as to induce a sensation of fullness of the patient's stomach, upon sensing an excessive level of food consumption (i.e., exceeding the predetermined level in the selected time interval, by integrating the number of swallows of food over that interval).
U.S. Pat. No. 5,540,734 (Cyberonics, Inc.) discloses that treatment, control or prevention of several medical, psychiatric or neurological disorders may be accomplished by application of modulating electric signals to one or both of a patient's trigeminal and glossopharyngeal nerves. Among the treatable disorders are eating disorders including anorexia nervosa, bulimia and compulsive overeating.
U.S. Pat. No. 5,782,798 (Medtronic, Inc.) reports that the neural circuitry of the brain that controls eating and satiety includes neurons in the lateral hypothalamus (feeding) and the ventral medial hypothalamus (satiety). Certain techniques using drugs and electrical stimulation for treating an eating disorder by means of an implantable signal generator and electrode and an implantable pump and catheter are described. The catheter is surgically implanted in the brain to infuse drugs and the electrode is implanted in the brain to provide electrical stimulation. Stimulation sites in the brain include the lateral hypothalamus, the paraventricular nucleus and the ventral medial hypothalamus.
U.S. Patent Application Publication No. 2005/0027284 (Advanced Neuromodulation Systems, Inc.) proposes alleviation or modulation of mood and/or anxiety disorders by stimulation of subcallosal areas of the brain, such as subgenual cingulate area, subcallosal gyrus area, ventral/medial prefrontal cortex area, ventral/medial white matter, Brodmann area 24, Brodmann area 25, and/or Brodmann area 10.
New ways to treat patients suffering from severe or life threatening eating disorders that are not sufficiently responsive to conventional therapies are needed.